Blender Mesh is deforming when imported into Unity3D
Your model has subsurface modifier applied after the animation deformation which didn't get applied when you exported your model.

So you should apply your subsurface modifier before you export your model.

But,Your subsurface modifier should be at the top of the modifier stack in order to work correctly in Unity as you see it in blender.

So move your subsurface modifier at the top after the skin modifier and apply it.